This initial test of the effects of MDCFs on microbiota immaturity and host responses to dietary intervention will provide key datasets that will enable a power calculation for our planned proof of concept study in a larger population. In the current exploratory pre-POC each child in each group of 12-15 study participants will serve as his/her own control. Additional comparisons will be made within and across the four treatment groups (i.e., those consuming reference RUSF standard, and one of three different MDCF formulations).